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Friendliness: It’s in the genes

The two genes regulate oxytocin, considered the supreme human social hormone, and are associated with a young adult's social skills and number of friends

Why are some people more sociable while others prefer solitude? The answer could be found in two genes that regulate oxytocin hormone in our bodies.

A study by NUS researchers has discovered that a higher expression of the CD38 gene and the presence of differences in the CD157 gene sequence are associated with a person having more close friends and better social skills. The findings were published in the scientific journal Psychoneuroendocrinology.

Conducted by Professor Richard Ebstein and his recent PhD graduate Dr Anne Chong, both from NUS Psychology and part of the Behavioural and Biological Economics and the Social Sciences (B2ESS) Group at NUS Arts and Social Sciences, the study recruited 1,300 Chinese young adults in Singapore. The researchers investigated how the expression of CD38 in the participants and the sequence changes of CD157 gene correlated with their social skills. The social skills of the participants were evaluated using questionnaires which appraised their ability to engage in social relationships, the quality of their friendships and the value that is placed on them.

Many gene studies often only focus on the structural changes in the gene sequences and how that could affect a particular characteristic of a disease, Prof Ebstein shared. However, his team believes that studying gene expression — how much of the gene is produced in the body — would capture more information than simple structural studies on DNA sequences.

“It is the expression of genes that ultimately determine how a gene impacts our traits,” he said.

CD157 and CD38 genes regulate the release of oxytocin into the body. Oxytocin is the key social hormone that is involved in primary social behaviours including pair-bonding, mating and child-rearing, as well as the more complex behaviours such as empathy, trust and generosity. Hence, the team saw good incentive to study the oxytocin network in relation to social skills important for friendships.

This knowledge would be helpful in coming up with future intervention therapies or targeted treatments to achieve desirable outcomes for individuals with special needs.

— Prof Richard Ebstein

Results of the study revealed that a higher expression of CD38 is associated with a larger number of close friends, especially in male participants.

“Male participants with the higher gene expressions displayed greater sociality such as preferring activities involving other people over being alone, better communication and empathy-related skills compared to the other participants. Meanwhile, participants with lower CD38 expression reported less social skills such as difficulty in ‘reading between the lines’ or engaging less in social chitchat, and tend to have fewer friends,” said Dr Chong.

The study also showed that a change in the sequence of CD157 was associated with the participants’ interest in socialising and building relationships. Additionally, it correlated with increased expression of CD38 in the bloodstream as well as increased levels of oxytocin in the body.

Together, the higher expression of CD38 and the structural changes of CD157 would explain about 14 per cent of the variance in social skills in the general population, shared the researchers. This number is a far cry from the two per cent that studies only focusing on structural changes usually explain.

“In our study, we see that an individual’s genetic makeup could only go so far as predicting one’s social predisposition but does not necessarily trigger the trait since, in the end, it is the expression of gene that determines so. This knowledge would be helpful in coming up with future intervention therapies or targeted treatments to achieve desirable outcomes for individuals with special needs,” said Prof Ebstein.

A possible intervention therapy could involve new drugs that mimic or enhance the functions of the CD38 and CD157 genes to help with improvement of social skills for people with autism, the researchers suggested. While this route has yet to be explored, therapies based on these findings could eventually allow people with extreme difficulty maintaining social and working relationships live a better quality of life.

From left: Dr Chong and Prof Ebstein

This study is part of a larger scope of research the B2ESS Group is conducting. Co-led by Prof Ebstein and Professor Chew Soo Hong from NUS Economics, along with Professor Lai Poh San from NUS Yong Loo Lin School of Medicine, the group has been investigating the role of genes and hormones on human behaviours, decision making, and a variety of human attitudes including empathy, impulsivity, political attitudes, religiosity and risk attitudes.

In the near future, the group will be embarking on several behavioural economics and molecular genetic studies to further investigate the impact of oxytocin on other human traits, such as creativity.